The invention relates, in general, to movable barrier operators and, in particular, to garage door operators having systems for receiving radio frequency transmissions that are encoded or encrypted to identify an authorized user of one or more transmitters.
A number of systems already exist for the control of movable barrier garage door operators using radio frequency transmitters. For instance, U.S. Pat. No. 4,750,118 discloses a transmitter for transmitting a multiple bit code which, when received and decoded by a receiver, causes the receiver to command a motor to open or close a garage door. Other systems, such as that disclosed in U.S. Pat. No. 3,906,348, employ a transmitter and a receiver wherein a plurality of mechanical switches may be used to establish a stored authorization code.
U.S. Pat. No. 4,529,980 to Liotine et al. discloses a transmitter and receiver combination for use in a garage door operator wherein the transmitter is able to store an authorization code which is to be transmitted to and received by the receiver over a radio frequency link. In order to alter or update the authorization code contained within the transmitter, the receiver is equipped with a programming signal transmitter or light emitting diode that can send a digitized optical signal back to the transmitter where it is stored. Other systems employing coded transmissions are disclosed in U.S. Pat. Nos. 4,037,201, 4,535,333, 4,638,433 and 4,988,992.
While each of these systems has in the past provided good security for operational use, they are relatively inconvenient or insecure for a user who wishes to establish a new fixed code for storage in a receiver. Many of the currently-available garage door operators include equipment that enables the receiver to learn a particular code. However, they are relatively inconvenient to use because they must be accessed by pressing a learn code button located on the head unit of the receiver which, of course, is normally mounted from the ceiling of the garage. Thus, the user would have to climb a step ladder, push the learn button and then either send newly encoded signals from an outside keypad or from a transmitter. If the apparatus does not employ an actuator which would cause a door to be moved, but relates, for instance, to an automotive security system, the learn button of necessity must be made even more inaccessible than the learn button on a garage door operator. For instance, an auto security system learn button might be positioned someplace underneath a locked hood or the like. Thus, it is very inconvenient, due to security requirements, to obtain access to the learn button.
What is needed then is an improved movable barrier operator or other type of actuator system employing coded transmissions which provide good security while enabling a code to be easily and conveniently altered.